/*
-----------------------------------------------------------------------------
This source file is part of OGRE
    (Object-oriented Graphics Rendering Engine)
For the latest info, see http://www.ogre3d.org/

Copyright (c) 2000-2012 Torus Knot Software Ltd

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
-----------------------------------------------------------------------------
*/
#ifndef VECTOR2_H
#define VECTOR2_H

#include <iosfwd>

/** Standard 2-dimensional vector.
    @remarks
        A direction in 2D space represented as distances along the 2
        orthogonal axes (x, y). Note that positions, directions and
        scaling factors can be represented by a vector, depending on how
        you interpret the values.
*/
class Vector2
{
public:
    float x, y;

public:
    inline Vector2()
    {
    }

    inline Vector2(const float fX, const float fY )
    : x( fX ), y( fY )
    {
    }

    /** Exchange the contents of this vector with another. 
    */
    inline void swap(Vector2& other)
    {
        std::swap(x, other.x);
        std::swap(y, other.y);
    }

    /** Assigns the value of the other vector.
        @param
            rkVector The other vector
    */
    inline Vector2& operator = ( const Vector2& rkVector )
    {
        x = rkVector.x;
        y = rkVector.y;

        return *this;
    }

    inline Vector2& operator = ( const float fScalar)
    {
        x = fScalar;
        y = fScalar;

        return *this;
    }

    inline bool operator == ( const Vector2& rkVector ) const
    {
        return ( x == rkVector.x && y == rkVector.y );
    }

    inline bool operator != ( const Vector2& rkVector ) const
    {
        return ( x != rkVector.x || y != rkVector.y  );
    }

    // arithmetic operations
    inline Vector2 operator + ( const Vector2& rkVector ) const
    {
        return Vector2(
            x + rkVector.x,
            y + rkVector.y);
    }

    inline Vector2 operator - ( const Vector2& rkVector ) const
    {
        return Vector2(
            x - rkVector.x,
            y - rkVector.y);
    }

    inline Vector2 operator * ( const float fScalar ) const
    {
        return Vector2(
            x * fScalar,
            y * fScalar);
    }

    inline Vector2 operator * ( const Vector2& rhs) const
    {
        return Vector2(
            x * rhs.x,
            y * rhs.y);
    }

    inline Vector2 operator / ( const float fScalar ) const
    {
        assert( fScalar != 0.0 );

        float fInv = 1.0f / fScalar;

        return Vector2(
            x * fInv,
            y * fInv);
    }

    inline Vector2 operator / ( const Vector2& rhs) const
    {
        return Vector2(
            x / rhs.x,
            y / rhs.y);
    }

    inline const Vector2& operator + () const
    {
        return *this;
    }

    inline Vector2 operator - () const
    {
        return Vector2(-x, -y);
    }

    // overloaded operators to help Vector2
    inline friend Vector2 operator * ( const float fScalar, const Vector2& rkVector )
    {
        return Vector2(
            fScalar * rkVector.x,
            fScalar * rkVector.y);
    }

    inline friend Vector2 operator / ( const float fScalar, const Vector2& rkVector )
    {
        return Vector2(
            fScalar / rkVector.x,
            fScalar / rkVector.y);
    }

    inline friend Vector2 operator + (const Vector2& lhs, const float rhs)
    {
        return Vector2(
            lhs.x + rhs,
            lhs.y + rhs);
    }

    inline friend Vector2 operator + (const float lhs, const Vector2& rhs)
    {
        return Vector2(
            lhs + rhs.x,
            lhs + rhs.y);
    }

    inline friend Vector2 operator - (const Vector2& lhs, const float rhs)
    {
        return Vector2(
            lhs.x - rhs,
            lhs.y - rhs);
    }

    inline friend Vector2 operator - (const float lhs, const Vector2& rhs)
    {
        return Vector2(
            lhs - rhs.x,
            lhs - rhs.y);
    }

    // arithmetic updates
    inline Vector2& operator += ( const Vector2& rkVector )
    {
        x += rkVector.x;
        y += rkVector.y;

        return *this;
    }

    inline Vector2& operator += ( const float fScaler )
    {
        x += fScaler;
        y += fScaler;

        return *this;
    }

    inline Vector2& operator -= ( const Vector2& rkVector )
    {
        x -= rkVector.x;
        y -= rkVector.y;

        return *this;
    }

    inline Vector2& operator -= ( const float fScaler )
    {
        x -= fScaler;
        y -= fScaler;

        return *this;
    }

    inline Vector2& operator *= ( const float fScalar )
    {
        x *= fScalar;
        y *= fScalar;

        return *this;
    }

    inline Vector2& operator *= ( const Vector2& rkVector )
    {
        x *= rkVector.x;
        y *= rkVector.y;

        return *this;
    }

    inline Vector2& operator /= ( const float fScalar )
    {
        assert( fScalar != 0.0 );

        float fInv = 1.0f / fScalar;

        x *= fInv;
        y *= fInv;

        return *this;
    }

    inline Vector2& operator /= ( const Vector2& rkVector )
    {
        x /= rkVector.x;
        y /= rkVector.y;

        return *this;
    }

    /** Returns the length (magnitude) of the vector.
        @warning
            This operation requires a square root and is expensive in
            terms of CPU operations. If you don't need to know the exact
            length (e.g. for just comparing lengths) use squaredLength()
            instead.
    */
    inline float length () const
    {
        return sqrt( x * x + y * y );
    }

    /** Returns the square of the length(magnitude) of the vector.
        @remarks
            This  method is for efficiency - calculating the actual
            length of a vector requires a square root, which is expensive
            in terms of the operations required. This method returns the
            square of the length of the vector, i.e. the same as the
            length but before the square root is taken. Use this if you
            want to find the longest / shortest vector without incurring
            the square root.
    */
    inline float squaredLength () const
    {
        return x * x + y * y;
    }

    /** Returns the distance to another vector.
        @warning
            This operation requires a square root and is expensive in
            terms of CPU operations. If you don't need to know the exact
            distance (e.g. for just comparing distances) use squaredDistance()
            instead.
    */
    inline float distance(const Vector2& rhs) const
    {
        return (*this - rhs).length();
    }

    /** Returns the square of the distance to another vector.
        @remarks
            This method is for efficiency - calculating the actual
            distance to another vector requires a square root, which is
            expensive in terms of the operations required. This method
            returns the square of the distance to another vector, i.e.
            the same as the distance but before the square root is taken.
            Use this if you want to find the longest / shortest distance
            without incurring the square root.
    */
    inline float squaredDistance(const Vector2& rhs) const
    {
        return (*this - rhs).squaredLength();
    }

    /** Calculates the dot (scalar) product of this vector with another.
        @remarks
            The dot product can be used to calculate the angle between 2
            vectors. If both are unit vectors, the dot product is the
            cosine of the angle; otherwise the dot product must be
            divided by the product of the lengths of both vectors to get
            the cosine of the angle. This result can further be used to
            calculate the distance of a point from a plane.
        @param
            vec Vector with which to calculate the dot product (together
            with this one).
        @return
            A float representing the dot product value.
    */
    inline float dotProduct(const Vector2& vec) const
    {
        return x * vec.x + y * vec.y;
    }

    /** Normalises the vector.
        @remarks
            This method normalises the vector such that it's
            length / magnitude is 1. The result is called a unit vector.
        @note
            This function will not crash for zero-sized vectors, but there
            will be no changes made to their components.
        @return The previous length of the vector.
    */
    inline float normalise()
    {
        float fLength = sqrt( x * x + y * y);

        // Will also work for zero-sized vectors, but will change nothing
        // We're not using epsilons because we don't need to.
        // Read http://www.ogre3d.org/forums/viewtopic.php?f=4&t=61259
        if ( fLength > float(0.0f) )
        {
            float fInvLength = 1.0f / fLength;
            x *= fInvLength;
            y *= fInvLength;
        }

        return fLength;
    }

    /** Returns a vector at a point half way between this and the passed
        in vector.
    */
    inline Vector2 midPoint( const Vector2& vec ) const
    {
        return Vector2(
            ( x + vec.x ) * 0.5f,
            ( y + vec.y ) * 0.5f );
    }

    /** Returns true if the vector's scalar components are all greater
        that the ones of the vector it is compared against.
    */
    inline bool operator < ( const Vector2& rhs ) const
    {
        if( x < rhs.x && y < rhs.y )
            return true;
        return false;
    }

    /** Returns true if the vector's scalar components are all smaller
        that the ones of the vector it is compared against.
    */
    inline bool operator > ( const Vector2& rhs ) const
    {
        if( x > rhs.x && y > rhs.y )
            return true;
        return false;
    }

    /** Sets this vector's components to the minimum of its own and the
        ones of the passed in vector.
        @remarks
            'Minimum' in this case means the combination of the lowest
            value of x, y and z from both vectors. Lowest is taken just
            numerically, not magnitude, so -1 < 0.
    */
    inline void makeFloor( const Vector2& cmp )
    {
        if( cmp.x < x ) x = cmp.x;
        if( cmp.y < y ) y = cmp.y;
    }

    /** Sets this vector's components to the maximum of its own and the
        ones of the passed in vector.
        @remarks
            'Maximum' in this case means the combination of the highest
            value of x, y and z from both vectors. Highest is taken just
            numerically, not magnitude, so 1 > -3.
    */
    inline void makeCeil( const Vector2& cmp )
    {
        if( cmp.x > x ) x = cmp.x;
        if( cmp.y > y ) y = cmp.y;
    }

    /** Generates a vector perpendicular to this vector (eg an 'up' vector).
        @remarks
            This method will return a vector which is perpendicular to this
            vector. There are an infinite number of possibilities but this
            method will guarantee to generate one of them. If you need more
            control you should use the Quaternion class.
    */
    inline Vector2 perpendicular(void) const
    {
        return Vector2 (-y, x);
    }

    /** Calculates the 2 dimensional cross-product of 2 vectors, which results
        in a single floating point value which is 2 times the area of the triangle.
    */
    inline float crossProduct( const Vector2& rkVector ) const
    {
        return x * rkVector.y - y * rkVector.x;
    }

    /** Returns true if this vector is zero length. */
    inline bool isZeroLength(void) const
    {
        float sqlen = (x * x) + (y * y);
        return (sqlen < (1e-06 * 1e-06));

    }

    /** As normalise, except that this vector is unaffected and the
        normalised vector is returned as a copy. */
    inline Vector2 normalisedCopy(void) const
    {
        Vector2 ret = *this;
        ret.normalise();
        return ret;
    }

    /** Calculates a reflection vector to the plane with the given normal .
    @remarks NB assumes 'this' is pointing AWAY FROM the plane, invert if it is not.
    */
    inline Vector2 reflect(const Vector2& normal) const
    {
        return Vector2( *this - ( 2 * this->dotProduct(normal) * normal ) );
    }

    /// Check whether this vector contains valid values
    inline bool isNaN() const
    {
        // std::isnan() is C99, not supported by all compilers
        // However NaN always fails this next test, no other number does.
        return (x != x) || (y != y);
    }

    /** Function for writing to a stream.
    */
    inline friend std::ostream& operator<<(std::ostream& o, const Vector2& v)
    {
        o << "Vector2(" << v.x << ", " << v.y <<  ")";
        return o;
    }
};

#endif // VECTOR2_H
